Back in the early days of games, programmers were having enough trouble creating a working product, putting all of their work (and processing power) into gameplay and graphical output. From the earliest, Tennis for Two, to more sophisticated early games like Galaga, there was either very little music (usually in the form of title screen jingles) or no music at all. It makes sense; this was back when the limits of gaming technology mandated that designers carefully choose how each bit of data was consumed. They just didn't have the space to worry about music when they were having enough trouble getting the game to run.
As shocking as that may seem now.